Abstract: This study investigated the adsorption of chloramphenicol by microplastics in water and examined the effects of the combined pollutant on zebrafish gut microbiota using high-throughput 16S rRNA sequencing. The results demonstrated that the equilibrium adsorption capacity of chloramphenicol by microplastics was 2.27 mg/g, consistent with a quasi-first-order kinetic model, while the saturated adsorption capacity was 14.60 mg/g, aligning with the Langmuir adsorption model. Gut microbiota analysis revealed that in the experimental group exposed to the microplastic-antibiotic composite pollutant, the abundance of Bacteroidota and Firmicutes increased progressively, whereas the abundance of Proteobacteria and Fusobacteriota showed minimal changes. Additionally, microbial beta-diversity was significantly reduced. This study confirms that microplastics can act as carriers of chloramphenicol, enter aquatic organisms, and alter the structure of the intestinal microbial community.